Due to increasing scarcity of fluid fossil fuels such as oil and natural gas, much attention is being directed towards converting solid carbonaceous materials such as coal, oil shale, and solid waste to liquid and gaseous hydrocarbons by pyrolyzing the solid carbonaceous material. Typically, pyrolysis occurs under non-oxidizing conditions in the presence of a particulate source of heat.
In the past, pyrolysis has been carried in tubular reactors. While effective, the yield of middle boiling hydrocarbons, i.e. C.sub.5 hydrocarbons to hydrocarbons having an end point of about 950.degree. F has been less than desired. Their loss has been attributed to protracted effective pyrolysis times which result in thermal cracking of such hydrocarbons. A need exists therefore for a more efficient pyrolysis process which maximizes the yield of the middle boiling hydrocarbons which are useful for the production of gasoline, diesel fuel, heating oil, and the like.